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HVAC Systems Overview

HVAC Systems Overview

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HVAC Systems Overview

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  1. HVAC Systems Overview HVAC Overview - # 1

  2. Agenda • Psychrometric questions? • Larger ‘psycho’ chart • Email address list • Project teams formed… topics? • Overview of HVAC systems, types HVAC Overview - # 2

  3. HVAC Systems Overview • External Factors • Ambient temperature, humidity • Solar radiation • Wind Equipment • Internal Factors • Occupants • Moisture gains • Acceptable environment (comfort, health and safety) • Internal air distribution HVAC Overview - # 3

  4. General Design Issues with HVAC • Determine required indoor conditions • Temperature and humidity levels • Ventilation • Determination of loads (cooling or heating) • Heat transmission through building shell • Heat gains from occupants • Heat gains from lighting and equipment • Ventilation and infiltration/exfiltration • HVAC system type • Building size, # of subdivisions • Local energy prices • Local climate • Initial cost versus life cycle cost • Other considerations • Energy usage • Indoor air quality HVAC Overview - # 4

  5. Type of Systems • All air • Water / air • All water • Centralized versus decentralized HVAC Overview - # 5

  6. Typical thermodynamic processes Cooling and dehumidifying moist air Evaporative cooling Humidity Ratio (W)   Dry Bulb Temperature Zone conditions,    Nearly saturated supply,   Ambient HVAC Overview - # 6

  7. Typical processes (Cont’d) Heating     Ambient Ambient,  Zone conditions,  Mixed zone/ambient,  Heating to supply air, HVAC Overview - # 7

  8. Direct Expansion Air Conditioning Outdoor Air COND Expansion Valve Compressor EVAP Supply Air Return Air Mixed Air Outdoor Air HVAC Overview - # 8

  9. Common System Types Central systems, Variable Air Volume (VAV) Exhaust Air Return Fan VAV Supply Conditioning Coils Ventilation Air Supply Fan HVAC Overview - # 9

  10. Common System Types Central systems, Dual Duct Heating Coil (Hot Deck) Exhaust Air Return Fan Mixing Boxes Filters Ventilation Air Cooling Coil (Cold Deck) Supply Fan HVAC Overview - # 10

  11. Common System Types Fan Coil Units (Unit Ventilator) Supply Air Supply Fan Cooling Coil Heating Coil Drain Pan Filters Ventilation Air Return Air HVAC Overview - # 11

  12. Common System Types Packaged Unit (Rooftop or Sidewall) Direct Expansion Cooling Heat Pump or Gas Fired Heating Supply Air Return Air Alternate Supply and Return Ductwork HVAC Overview - # 12

  13. Common System Types Split-System Return Air Condensing Unit Furnace Evaporator Refrigerant Lines Supply Air HVAC Overview - # 13

  14. Chilled Water Systems Cooling Tower Chiller Chilled Water System  Various System Loads (Coils) HVAC Overview - # 14

  15. Energy Recovery from Ventilation Air • One common approach is enthalpy wheel Exhaust Intake Outdoor Air Exhaust Air Cooling Mode Supply Air Return Air Heating Mode Supply Air Return Air OA Exhaust Air HVAC Overview - # 15

  16. Economizer Systems Exhaust Air Return Air Recirculation Air Supply Air @ Mixed Conditions Outdoor Air • Get ‘free cooling’ by using up to 100% outdoor air supply to room • Controllers use enthalpy (T and H) or temperature only for control decision HVAC Overview - # 16

  17. Economizer Systems    Ambient Ambient,  Zone conditions,  Mixed zone/ambient,  Mixed air conditions: Cooling provided to building: HVAC Overview - # 17